Methods for using solar energy to heat fluids are well known in the art. In particular, methods employing a solar energy absorber panel in thermal contact with fluid conduits are well known. For example, Godrick, U.S. Pat. No. 3,987,784, owned by the assignee of this application, describes and claims a solar energy absorber panel utilizing a thin, energy absorbing sheet in thermal contact with a plurality of fluid conduits. The conduits are arranged in a parallel array extending the length of the panel, and are shaped to provide a large area of thermal contact between the conduits and the absorber panel. In Godrick, each fluid conduit has a flat side which is bonded to the surface of the thin solar energy absorber panel.
When a solar energy absorber panel, such as that described by Godrick, is used to provide hot water from a relatively high pressure source, such as city line pressure (50 to 125 psig), the substantially rectangular cross-sectional conduits described in Godrick should probably not be used. In their place, a conduit having a circular cross section should be used to better withstand the higher pressures.
Indeed, conduits having circular cross sections have been used by others to provide a solar heating system for hot water. The conduits are generally connected to the energy absorbing panel by a thermally conductive cement, paint, or solder to provide as much thermal contact as possible. However, many of the fabrication methods employed by these prior art systems are expensive, because they require elaborate tooling to form the panels. Other methods require heavier weight panels than those described in Godrick, thereby increasing the cost and weight per unit, and still others are uneconomical because the number of steps in the fabrication process increases the cost per unit. Some prior art methods are described in Godrick as well as: Edmondson, U.S. Pat. Nos. 3,952,725; Patil, 3,974,822; Jarkin, 3,384,167; Beck, 3,698,475; Gallagher, 3,972,317; and Barber, Jr., 3,980,071.
Therefore, principle objects of this invention are a method for making a solar heating unit utilizing circular cross section conduits which is simple to implement, which requires few process steps, which is substantially self-aligning, which is reliable, and which provides a significant area of contact between the conduits and the absorber panel. Other objects of the invention include a method which results in a low cost, low weight unit, which does not require complicated or expensive tools and dies, and which can be easily implemented on a mass production basis.
Another object of the invention is to provide a method which results in a solar absorber panel which requires a minimum of material components.